1. Field of the Invention
The present invention relates to a die-level prober, and more particularly, to a die-level prober for testing unpackaged liquid crystal on silicon (LCOS) display panels.
2. Description of the Prior Art
A liquid crystal on silicon (LCOS) display panel has the advantages of small pixels, high brightness, high resolution, simple and low-cost fabrication, a small volume and so forth. Accordingly, the LCOS display panel is used widely in video communication devices and video equipment. For example, the video communication devices could be portable-type cameras and web cellular phones, and the video equipment could be projection televisions and multimedia projectors.
Please refer to FIG. 1 and FIG. 2. FIG. 1 shows a conventional method for fabricating an LCOS display panel. FIG. 2 shows a side view of an unpackaged LCOS display panel. Initially, with reference to FIG. 1 and FIG. 2, providing a semiconductor substrate 10, the semiconductor substrate 10 includes a plurality of dies 14 and a plurality of pads 26. Each die 14 contains an active matrix array (not shown) for a pixel circuit of an LCOS display panel. The pads 26 are electrically connected with the LCOS display panel to an exterior circuit. Next, an alignment film 20a is formed on a surface of the semiconductor substrate 10. A seal pattern 22 is then formed in the peripheral region of each die 14.
Next, a glass substrate 12 is provided in parallel with the semiconductor substrate 10. A conductive photo-resist layer 18 and an alignment film 20b are subsequently formed. The conductive photo-resist layer 18 is used as a common electrode and a color filter. The alignment films 20a and 20b are used for adjusting the orientation of liquid crystal molecules, and they include the materials polyimide resin, SiO2, or SiNx. Then, an assembly process is performed to bind the glass substrate 12 onto the semiconductor substrate 10 through each seal pattern 22. The glass substrate 12 and the semiconductor substrate 10 are sawed into individual LCOS display panels along each scribe line 13 of the glass substrate 12 and each scribe line 11 of the semiconductor substrate 10. Then, a liquid crystal filling process is performed to fill the liquidcrystal molecules between the glass substrate 12 and the semiconductor substrate 10, so as to form a liquid crystal layer 24 between the glass substrate 12 and the semiconductor substrate 10 to finish individual LCOS display panel 16. Finally, a package process is performed to package individual LCOS display panel 16 into a display component of electric devices.
It is noted that the yields of forming the conductive photo-resist layer 18 on the glass substrate 12 and binding the glass substrate 12 onto the semiconductor substrate 10 are low. Therefore, the LCOS display panel 16 often has defects and the display quality of the panel is reduced or the panel is unable to display. With reference to FIG. 2, as for the unpackaged LCOS display panel 16, the conductive photo-resist layer 18 of the glass substrate 12 and the contact pad 26 of the semiconductor substrate 10 are located on opposite sides, but a prober commonly used at present cannot do an electrical test for such LCOS display panel 16. Accordingly, an LCOS display panel 16 having defects that are generated prior to the package process is often discovered after the package process, which increases the cost of the package process and reduces the quality of the package process. As a result, providing a die-level prober for testing an unpackaged LCOS display panel 16 is important for resolving the above problem.